[68 P.O.S.]

Good deal on the shroud, that has a huge effect on cooling. Are you sure the rad is good to go? A 4 row should be plenty. Could be clogged just enough to reduce it's efficiency maybe. The rad is the main part of your cooling system, do you know anything about yours?

Bump your timing back up to 12 or 14 and readjust your idle. If you trust your temp gauge that's good enough for me. You can get an IR thermometer to double check it.

Yes, check your vac advance. Make sure the weights move freely & are lubed and make sure the vac can diaphragm isn't leaking or blown out. Easy check...hook it up to manifold vacuum and the idle will jump noticeably. If it doesn't, the vac can is bad or you already had it hooked up to manifold.